polymorphisms correlated with drug activity or prognosis after EGFR-TKI treatment in NSCLC (Tables 1 &
2).
Table 2. Clinical studies on polymorphisms correlated with prognosis after gefitinib/erlotinib treatment
Study Num.
patients Studied
Polymorphisms Effects Ref.
Liu G, et al.
2008
92 EGFR: 216G/T,191C/A, Intr1, R497K
-216G/T:T allele is associated with longer PFS, increased SD/PR and risk of developing rash and diarrhea
-Intr1 homozygosis of short allele associated with longer PFS and OS 27
Ichiara T, et
al. 2007 98 EGFR: 216G/T,191C/A, Intr1, mut, copy-num; KRAS:
mut
-EGFR mut are associated with longer PFS and OS
-short Intr1 increased OS in EGFR mutated patients 28 Gregorc V,
et al. 2008
170 EGFR: 216G/T,191C/A -G-C haplotype is associated with reduced RR 29 Han SW, et
al. 2007
86 EGFR: Intr1, mut -short Intr1 is associated with higher RR and increased TTP - EGFR mut are associated with longer OS
34 Ma F, et al.
2009
84 Whole gene based-tag SNP -EGFR rs2293347GG(D994D) is associated with higher RR and longer PFS than GA and AA
-short Intr1 is associated with higher RR
35
Dubey S, et
al. 2006 157 EGFR: Intr1 -short Intr1 is associated with squamous cell histology
-long Intr1 is associated with longer OS 36
Nie Q, et al.
2007 70 EGFR: Intr1, R497K -short Intr1 is associated with higher EGFR expression, higher RR and
longer PFS 37
Tiseo M, et
al. 2008 58 EGFR: Intr1, mut, copy-num -short Intr1 is associated with longer OS 38 Tiseo M, et
al. 2010 91 EGFR: Intr1, mut, copy-num, expression;
KRAS: mut;
HER2: copy-num
-EGFR mut and copy-num are associated with higher RR
-short Intr1 is associated with longer OS 39
Giovannetti
E, et al. 2010 96 EGFR: 216G/T,191C/A, R497K, Intr1, mut;
KRAS: mut;
AKT1-SNP4
-EGFR mut are associated with higher RR, TTP and OS -216G/T, 191C/A and R497K are associated with higher risk of developing grade>1 diarrhea
-AKT1-SNP4 A/A is associated with reduced TTP and OS
40
Liu G, et al.
2012 242 EGFR: 216G/T,191C/A, Intr1;
ABCG2: 421C>A;
AKT1-SNP4G>A
-long Intr1 is associated with reduced PFS
-216T/T genotype is associated with higher risk of developing rash 41
Cappuzzo F,
et al. 2004 106 Akt: activation; MAPK:
activation -p-Akt is associated with higher RR, DCR and TTP 44 Cappuzzo F,
et al. 2007 42 EGFR: mut, copy-num;
KRAS: mut; HER2: mut, copy-num; Akt: activation
-EGFR high copy-num is associated with higher RR, TTP and OS 45
Kim MJ, et
al. 2012 310 AKT1: rs3803300, rs1130214, rs3730358, rs1130233, rs2494732
-rs3803300, rs1130214 and rs2494732 when combined are associated
with worse OS and PFS 50
Lemos C, et al. 2011
94 ABCG2: 15622C/T, 1143C/T -15622T/T and TT haplotype are associated with higher risk of developing grade 2/3 diarrhea
53 Han JY, et
al. 2011
158 XRCC1: codon 399; ERCC1:
codon 8092;
RRMI: codon 2464
-XRCC1 399Arg/Arg is associated with higher RR and longer PFS than Gln allele
-ERCC1 8092CA and RRMI 2464GG genotypes are associated with longer PFS
60
Huang CL, et
al. 2009 52 EGFR: 216G/T,191C/A,
R521K, Intr1 -homozygosis of short Intr1 is associated with higher risk of developing
early grade 2/3 rash 62
Rudin CM, et al. 2008
43 EGFR: 216G/T,191C/A, 497G/A; CYP3A4*1B;
CYP3A5*3; ABCG2: 421C/A, 34G/A, 15994G/A,
15622C>T, 16702G/A, 1143C/T
-15622C/T and 1143C/T: T allele is associated with lower ABCG2 expression
-216G/T and 191C/A are associated with higher risk of developing diarrhea
63
Cusatis G, et al. 2006
124 ABCG2: 421C>A (Q141K) -heterozygosis is associated with diarrhea 66 Brugger W,
et al. 2011
889 EGFR: Intr1, mut, copy-num and expression; KRAS: mut
-EGFR mut are associated with longer PFS -KRAS mut are associated with reduced PFS
69 Hamada A,
et al. 2012
50 ABCB1: 1236TT, 2677TT, 3435TT
-1236TT, 2677TT and 3435TT are associated with higher plasma concentration and risk of developing toxicity
72
Intr1, intron1; mut, mutations; copy-num, gene copy number.
Table 3. Gefitinib versus chemotherapy as first-line treatment fon NSCLC EGFR mutant patients Study
(Ref number) Study
Phase Population Treatment (num. of
patients) ORR
(%) Median PFS/TTP
(months) Median OS (months) IPASS
(Ref 21) Phase III EGFR mutation
positive Gefitinib (132) Carbo+Pac (129)
71.2 47.3 P<0.001
9.5 6.3 P<0.001
21.6 21.9 P=1.00 NEJSG002
(Ref 78) Phase III EGFR mutation
positive Gefitinib (115) Carbo+Pac (115)
73.7 30.7 P<0.001
10.8 5.4 P<0.001
30.5 23.6 P=0.31 WJTOG3405
(Ref 79)
Phase III EGFR mutation positive
Gefitinib (88) Cis+Doc (89)
62.1 32.2 P<0.0001
9.2 6.3 P<0.0001
30.9 NA P=0.211 Carbo, Carboplatin; Pac, Paclitaxel; Cis, Cisplatin; Doc, Docetaxel.
The regulatory regions of EGFR are located within the 5´-flanking region and intron 1, and both the EGFR-191C/A and -216G/T polymorphisms lie in the transcriptional start site of the promoter region, wherein multiple nuclear regulatory affinity sites are located. The -191C/A polymorphism has been correlated with enhanced EGFR promoter gene expression and activity, while the AG variant, which leads to the substitution of an arginine with a lysine at codon 497 (R497K), has been associated with reduction of EGFR activity [24,25]. Similarly, the -216G/T genotype is located in the binding site for the transcription factor Sp1, and the T allele is associated with increased EGFR mRNA expression [26]. The -216G/T, -191C/A and R497K EGFR polymorphisms were evaluated in a study conducted in 92 Caucasian advanced NSCLC patients treated with gefitinib and the association of the -216G/T variant with longer PFS was reported.
The T allele was also associated with significantly higher rates of stable disease/ partial response (p = 0.01) and a significantly higher risk of treatment-related rash/diarrhea (p = 0.004) [27]. A recent study in 98 Japanese NSCLC patients treated with gefitinib screened for EGFR mutations and polymorphisms -216G/T and -191C/A reported the mutations as predictive factors of sensitivity to gefitinib, overall survival (OS) and PFS, but no correlation was found between polymorphisms and clinical outcome [28]. In another study, 175 Caucasian NSCLC patients treated with gefitinib were screened for the same EGFR polymorphisms, and a significantly lower response rate was observed in patients carrying the GC haplotype [29].
A highly polymorphic region is also located in the EGFR intron 1 as 14–21 CA repeats [30]. Shorter alleles of this CA-repeat polymorphism, which are less common in Asian populations, are correlated with enhanced EGFR transcription [31]. In particular, the longer allele 21 has been reported to induce an 80%
decrease in the gene expression compared with the shorter allele 16 [32,33]. Most studies have reported a better response to gefitinib treatment in NSCLC patients harboring the short EGFR CA-repeat genotype [27–
29,34–36]. Ichihara and colleagues studied the relationship between clinical outcome and several genetic factors, including the EGFR CA-repeat variant, in 98 Japanese NSCLC patients treated with gefitinib. In this analysis, among patients with EGFR activating mutations, individuals carrying the shorter CA alleles had a trend toward a significantly longer OS (p = 0.13) compared with those with the long alleles (defining long CA repeats as ≥19, or the sum of two alleles ≥39, and short CA repeats as <19, or the sum of two alleles <39) [28]. Another study focused on the correlation of clinical outcome after gefitinib treatment with EGFR
mutations and CA-repeat genotype in 86 Korean patients with advanced NSCLC. In this investigation, short CA was defined as the sum of both alleles ≤37, while long CA was defined as the sum of both alleles ≥38. In agreement with the previous study, EGFR activating mutations were associated with sensitivity to gefitinib and OS, and short CA-repeat status was also correlated with better response and longer time to progression [34]. In a subsequent study performed by Nie et al. in 70 Chinese NSCLC patients treated with gefitinib, a significantly higher response rate was associated with shorter CA-repeat status (defined as any allele ≤16).
These patients also had higher EGFR expression and prolonged OS compared with those with long CA. No evidence of correlation with clinical outcome was reported for the R497K polymorphism or EGFR expression [37]. Shorter CA repeats (16 or less) were associated with significantly improved PFS and OS in another study in 92 Caucasian NSCLC patients who were treated with gefitinib [27]. Similarly, Tiseo et al. reported correlation of intron 1 EGFR (CA)16 status, including at least one (CA)16 allele, with survival in 91 Caucasian NSCLC patients treated with gefitinib [38]. However, in a second study performed by the same group, all the patients lacking the (CA)16 allele, except two EGFR-mutated patients (i.e., 18 out of the 76 evaluable patients), experienced rapid disease progression and shorter OS, suggesting a possible negative predictive value of (CA)16 allele absence in the response to gefitinib. No significant correlation was observed between (CA)n-repeat genotype and outcome [39].
Figure 1. Some of the most relevant polymorphisms in key genes involved in pharmacokinetics and pharmacodynamics of EGF receptor tyrosine kinase inhibitors correlated with gefitinib and erlotinib response and toxicity in non-small-cell lung cancer patients. EGFR: EGF receptor; TKI: Tyrosine kinase inhibitor.
In the largest pharmacogenetic analysis in Caucasian NSCLC patients treated with gefitinib (n = 175), no
association of the EGFR intron 1 CA-repeat status with clinical outcome was observed, grouping patients both with combined CA-repeat length on both alleles of ≤35 versus >35, and a CA-repeat length on both alleles of <18 versus all other [29].
In agreement with the previous analysis, in the authors’ study in 96 Caucasian NSCLC patients treated with gefitinib, it was observed that EGFR activating mutations were significantly associated with response, and longer time to progression and OS. By contrast, no correlation was found between EGFR intron 1 CA (for which patients were classified as S/S, L/L and S/L if the number of repeats was ≤16 on both alleles, >16 on both alleles and ≤16 on one allele and >16 on the other, respectively), -216G/T, -191C/A, and R497K polymorphisms and clinical outcome [40].
In order to investigate the correlation between different genotype variants in EGFR and therapeutic outcome and survival, a recent study used a whole-gene-based tag SNP approach in 84 Chinese NSCLC patients treated with gefitinib [35]. In this study, only the novel EGFR polymorphims rs2293347 (D994D) and intron 1 CA were associated with clinical response to the treatment. In particular, patients carrying the rs2293347 GG or shorter CA-repeat genotype (defined as ≤16 CA repeats) had more benefits from the treatment with gefitinib than those with the rs2293347 GA or AA or the longer CA-repeat variants. The rs2293347 GG genotype was also associated with a longer PFS compared with the rs2293347 GA or AA polymorphisms, whereas the combination of rs2293347 GG and shorter CA-repeat status showed the best clinical response.
The potential prognostic significance of EGFR intron 1 CA-repeat polymorphism was also evaluated in patients not treated with EGFR-TKIs. In particular, a recent study performed by Liu et al. reported a trend in significance for this polymorphism (hazard ratio [HR]: 1.7; p = 0.07]), whereby the longer alleles were associated with shorter PFS in a population of erlotinib-untreated patients. No other polymorphism was found to be as significantly prognostic for OS in the same study [41]. Conversely, the longer allele correlated with longer OS in a study performed in a US population (HR: 0.66; p = 0.03). On the basis of these results, the authors suggested that the allele length might predict the outcome in response to gefitinib [36]. Similar data were observed in a study of 30 pancreatic cancer patients; patients with a shorter sum of total CA repeats (<36) had significantly shorter median OS than patients with ≥36 repeats [42]. However, a more recent analysis performed by the same group in 135 pancreatic cancer patients revealed no correlation between EGFR intron 1 CA-repeat length and OS [43], suggesting that the prognostic role of this polymorphism might be related to a different tumor type.